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Vivek Sharma University of California at San Diego CP Violation in B 0 Decays: Some Highlights SheldonFest, May 20, 2006
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2 1987: Argus Discovers large B 0 B 0 Oscillation Rate ARGUS First time I heard the word CP violation and B mesons spoken together Started a chain of activities which ultimately led to the construction & operation of the asymmetric energy B factories Much skepticism initially about how well these machines would perform
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3 PEP-II Asymmetric B Factory & BaBar
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4 Machine Performance Exceeds Design (x3) 96% efficiency over the entire history of BABAR BABAR, Run 5 Peak luminosity (cm -2 s -1 ) 1.0025 x 10 34 Best shift247.2 pb -1 Best day710.5 pb -1 Best week4.464 fb -1 Best month17.036 fb -1 BABAR logged343 fb -1 KEK-B operation even more spectacular !
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5 BaBar Physics Productivity BaBar papers by topic: BaBar papers by area: Plan to exceed 220 publications by summer 2006 SubmittedBABARBelle Journal Papers201163 Publication Luminosity As of April 3 As of April 12 ‘06
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6 Direct CP Violation in B 0 K T P Loop diagrams from New Physics (e.g. SUSY) can modify SM asymmetry via Penguin diagram Need reliable knowledge of T/P and relative strong phase to extract / 3 Clean mode with a “large” rate: Measurement is a “Counting Experiment”
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7 Direct CP Violation in B 0 K : BaBar B0K+B0K+ B0K+B0K+ BABAR 4.2 , syst. included BABAR
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8 Rules out Superweak model Establishes CPV not just due to phase of B Mixing But hadronic uncertainties preclude determination of CKM angle challenge to theory Combined significance >> 6 Direct CP Violation in B 0 K : Belle (386M BB) Belle
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9 CPV In Interference Between Mixing and Decay + 2 + 2 B0B0 B0B0 B0B0 f cp B0B0 B0B0 B0B0 CP asymm. can be very large and “cleanly” related to CKM angles Requires time dependent measurement of CP Asymmetry
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10 Time-dependent CP Asymmetry Due to Interference in Mixing and Decay Phase of mixing Amplitude ratio (direct CPV)(indirect) ( for single weak decay amplitude)
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11 The “Platinum” Mode : B 0 J/ K 0 CP = -1 (+1) for J/ K 0 S(L)
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12 Visualizing Time-Dependent CPV Measurement
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Vivek Sharma, UCSD13 B 0 J/ K s z (4S) = 0.55 Coherent BB pair B0B0 B0B0 distinguish B 0 Vs B 0 distinguish B 0 Vs B 0 Steps in Time-Dependent CPV Measurement
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14 Effect of Mis-measurements on t Distribution Determine flavor mis- tag rates w and t resolution function R from large control samples of B 0 D (*) / /a 1, J/ K* BB Mixing PDF CP PDF perfect flavor tagging & time resolution realistic mis-tagging & finite time resolution
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15 B Charmonium Data Samples CP sampleN TAG purityη CP J/ψ K S (K S →π + π - )275196% J/ψ K S (K S →π 0 π 0 )65388% ψ(2S) K S (K S →π + π - )48587% χ c1 K S (K S →π + π - )19485% η c K S (K S →π + π - )28774% Total for η CP =-1437092% J/ψ K *0 (K *0 → K S π 0 )57277% J/ψ K L 278856% Total773078% M ES [GeV] ΔE [MeV] J/ψ K L signal J/ψ X background Non-J/ψ background B A B AR (η CP = +1)
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16 Sin(2 Result From B Charmonium K 0 Modes (2004) sin2β = 0.722 0.040 (stat) 0.023 (syst) (cc) K S modes (CP = 1) (PRL 89, 201802 (2002): sin(2β) = 0.741 ± 0.067 ± 0.034) J/ψ K L mode (CP = +1) hep-ex/0408127 background
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17 Belle 2005 (386M B B )
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19 The Unitarity Triangle Defined By CPV Measurements New B Factory milestone: Comparable UT precision from CPV in B decays alone
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20 UT With CPV & CP Conserving Measurements Incredible consistency between measurements ! Paradigm shift ! Look for NP as correction to the CKM picture
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21 Searching For NP >
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22 Compare sin2 with “sin2 ” from CPV in Penguin decays of B 0 Both decays dominated by single weak phase Penguin: Tree: New Physics? 33 ? Must be if one amplitude dominates
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23 Naïve Ranking Of Penguin Modes by SM “pollution” Bronze Gold SuperGold Decay amplitude of interestSM Pollution Naive (dimensional) uncertainties on sin2 Note that within QCD Factorization these uncertainties turn out to be much smaller !
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24 Penguin Lust ! Belle 140 fb -1 68±11 CP Asymmetry in B φ K S : LP2003 sin2φ 1eff = -0.96 ±0.50 3.5σ different ! Then WA: sin(2φ 1 ) c c s = 0.731±0.056 Belle
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25 New Physics ? Standard Model
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26 B 0 K 0 Since LP03 Modes with K S and K L are both reconstructed 114 ± 12 signal events98 ± 18 signal events full background continuum bkg (Opposite CP) Plots shown are ‘signal enhanced’ through a cut on the likelihood on the dimensions that are not shown, and have a lower signal event count hep-ex/0502019 BaBar: 222M B B
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27 CP analysis of ‘golden penguin mode’ B 0 K 0 S(K S ) = +0.29 ± 0.31(stat)S(K L ) = -1.05 ± 0.51(stat) Combined fit result Standard Model Prediction S(K 0 ) = sin2 = 0.69 ± 0.03 C(K 0 ) = 1-|| = 0 0.8 (Opposite CP) K0 BaBar
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28 Other (More Prolific) Golden penguin mode: B 0 ’K 0 Large statistics mode Reconstruct many modes – ’ + –, 0 – , + – 0 –K S + –, 0 0 B 0 ’K S 819 ± 38 signal events (K s mode) 440 ± 54 signal events (K L mode) hep-ex/0502017,0507087 B 0 ’K 0 sin2 [cc] @ 2.7 K0 BaBar ’K S
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31 Taken individually, each decay mode in reasonable agreement with SM but (almost) all measurements are lower than sin2 from c c s Naïve b s penguin average sin2 eff = 0.50 0.06 Theory models predict SM pollution to increase sin2 eff !!
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32 How good is the SM Theoretical Prediction? 2-body: Beneke, PLB 620 (2005) 143 3-body: Cheng, Chua & Soni, hep-ph/0506268 Calculations within framework of QCD factorization
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33 Direct CPV in s-Penguins ? No sign of direct CPV !
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34 What Are s-Penguins Telling Us ? This could be one of the greatest discoveries of the century, depending, of course, on how far down it goes… 2.4 discrepancy
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35 Possible Evolution by Summer 2008 K*K* 4 discovery region if non-SM physics is 0.19 effect 2004=240 fb -1 2008=1.0 ab -1 Individual modes reach 4-5 sigma level Projections are statistical errors only; but systematic errors at few percent level Luminosity expectations : 20082004 f 0 K S K S 0 K S ’K S KKK S
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36 An Optimist’s Global CKM fit ? : 2008 (1 fb -1 each) 95% contours ?
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Backup Slides
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38 Projected data sample growth: BaBar Expectation Integrated Luminosity [fb -1 ] 12 17 20 L peak = 9x10 33 oPEP-II: IR-2 vacuum, 2xrf stations, BPM work, feedback systems oBABAR: LST installation 4-month down for LCLS, PEP-II & BABAR Double from 2004 to 2006 ICHEP06 Double again from 2006 to 2008 ICHEP08
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39 ParameterUnitsDesignOct 20052007 goal I+mA214029404000 I-mA75017402200 Number of bunches16581732 y*y* mm15-20118-8.5 Bunch lengthmm1511-128.5-9 yy 0.030.044-0.0650.054-0.07 Luminosityx10 33 3.010.020 Int lumi / daypb -1 130727.81300 PEP-II overall parameters and goals 30%40% 10% Factor 2!
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40 Only More Data Can Reveal The True Picture Number of standard deviations Integrated luminosity (fb -1 ) KSKS ’K S average Assuming fluctuations around present central values BABAR 2008 BABAR+ Belle 2008 Possible evolution of deviations From SM
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Vivek Sharma, UCSD41 B 0 D 0 h 0 Belle’s New Method for Direct measurement of 1 _ (D 0 K S M(K S ) M(K S ) f -+ M(K S ) M(K S ) f +- A B0 D0h0 ( t) = cos( M t/2) sin( M t/2) -e i2 1 h0
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Vivek Sharma, UCSD42 Reconstruction of B 0 D[K S + - ]h 0 D 0 0 D 0 D 0 D *0 0, Nsig = 157 ±24 purity : 59% Nsig = 67 ±10 purity : 86% Nsig = 58 ±13 purity : 60% Nsig = 27 ±11 purity : 52% D *0 D 0 0 TOTAL Nsig = 309 ±31 purity : 63% _ D* D0 pi0 D*pi0 : 22 +- 9 D*eta : 5+- 6
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Vivek Sharma, UCSD43 Time-Dependent Dalitz fit results Final state 1 ( o ) D 0 0 11 ± 26 D 0 28 ± 32 D *0 0, 25 ± 35 combined 16 ±21(stat) ±11(syst) -30 o < 1 < 62 o (95% C.L.) Belle preliminary
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Vivek Sharma, UCSD44 Implications of Time-dependent Dalitz analysis 1 ~20 o 1 ~70 o sin2 1 11 ? ? (^_^) 2-fold ambiguity resolved ! Consistent with B 0 J/ K* results cos2 1 = 0.87 ±0.75, hep-ex/0504046 Disfavored >2
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47 A Completely Reconstructed (4S) Event at BaBar All particles accounted for Nothing Missing !
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48 An (4S) B B Event : Along The Beam Line Z
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49 Close Up of a Reconstructed (4S) B 0 B 0 Event
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50 Sin2b background BaBar 2004:Belle 2005:
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51 Three Kinds of CP Violation in B 0 Meson System Indirect CPV Direct CPV
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